Liquid crystal has been increasingly applied in a display panel due to good electrical controllability of itself. For a liquid crystal display panel, among liquid crystal display modes, the twisted nematic (TN) display mode is most widely used. However, according to the display principle of this display mode, the viewing angle is limited. As a solution to this problem, it is known to dispose a pixel electrode and a common electrode on a same substrate and apply a voltage between the pixel electrode and the common electrode, so that an electric field substantially parallel to the substrate is formed and liquid crystal molecules are driven in a plane substantially parallel to the substrate. Transverse electrical field modes are known to include the In-Plane Switching (IPS) mode and the Fringe Field Switching (FFS) mode. In the IPS mode, a comb-shaped pixel electrode and a comb-shaped common electrode are combined for an arrangement. In the FFS mode, an upper electrode layer and a lower electrode layer are disposed on a same substrate with an insulating layer disposed between the upper electrode layer and the lower electrode layer. Specifically, one of the upper electrode layer and the lower electrode layer is used as the common electrode, and the other is used as the pixel electrode. Moreover, the upper electrode layer is set to in a comb-shaped structure etc., with slit(s) formed therein as an opening portion for making the electrical field pass through.
Currently, it is widespread that the liquid crystal is used in the touch display panel of a display (i.e. liquid crystal display, LCD), which allows a user to touch the touch panel with a finger or other object, so as to input information into a device which uses the display panel. Thereby, the dependence of the user on other input device (such as the keyboard, mouse, remote control, etc.) can be reduced or eliminated to achieve a convenience operation for the user.
Early touch display panel is the resistive type. The pressure at the contact position between the touch body and the display panel makes two conductive films contact with each other, so as to close a certain switch and send a touch signal. However, in the case where the resistive touch display panel is repeatedly pressed for a long time, the two conductive films may deform with the repeated pressing, and thereby the performance of the two conductive films may degrade or even the two conductive films may be damaged, which is prone to cause misjudgment of the touch signal. For the above-mentioned disadvantage, the capacitive touch display panel is proposed.
As shown in FIG. 1, the basic structure of the touch layer of the capacitive touch display panel includes: a dielectric material, two conductive films which are isolated by the dielectric material from each other, a driving line 11 is disposed on the lower conductive film and a detecting line 12 is disposed on the upper conductive film. In the case where there is no touch made by the touch body, the equivalent circuit of the touch layer is as shown in FIG. 2. Specifically, a capacitance C1 is formed between the driving line 11 and the detecting line 12, and the driving line 11 and the detecting line 12 respectively has an equivalent resistance R2 and an equivalent resistance R3; the detecting line 12 is grounded via a resistance R1; the driving line 11 and the detecting line 12 respectively has a parasitic capacitance C2 and a parasitic capacitance C3 with respect to other conductive layer(s) of the display panel; the parasitic capacitance C2 of the driving line 11 is connected in series to the resistor R4 and then grounded; and the parasitic capacitance C3 of the detecting line 12 is connected in series to the resistance R5 and then grounded. In this case, if an alternate current signal I0 is applied to the driving line 11, the voltage Vs of a corresponding signal will be detected from the detecting line 12. In the case where the touch body (such as a finger) touches the touch layer, such as the detecting line 12, as shown in FIG. 3, the equivalent circuit of the touch layer is as shown in FIG. 4. Specifically, the finger 12 applies a grounding capacitance C5 to the detecting line 12, and the equivalent resistance of the finger is R6. In this case, if the alternate current signal I0 is still applied to the driving line 11, the voltage Vs of the corresponding signal detected from the detecting line 12 will be smaller, since the resistance R6, the grounding capacitance C5 and the capacitance C1 are connected in series sequentially. In summary, whether the touch layer is touched may be known according to the voltage detected from the detecting line 12.
Combining the above-mentioned IPS, FFS liquid crystal display and the capacitive touch display panel, the IPS, FFS liquid crystal display (FFS-LCD) touch display panel is formed and include(s): a color film (CF) substrate, a thin film transistor (TFT) substrate and a liquid crystal layer therebetween. The touch layer is disposed on the CF substrate. However, in the above-mentioned FFS-LCD touch display panel, the driving lines and the detecting lines are disposed all over the entire layer, and thus the driving lines and the detecting lines are completely overlapped with the upper electrode layer (the pixel electrode or the common electrode) having the comb-shaped structure respectively. The liquid crystal is filled between the driving and detecting lines and the upper electrode layer. The liquid crystal is equivalent to be the dielectric material, the driving lines and the detecting lines are equivalent to be one electrode plate, and the upper electrode layer having the slit(s) is equivalent to be the other electrode plate. Therefore, there may be parasitic capacitances existed between the driving lines and the upper electrode layer having the comb-shaped structure, and between the detecting lines and the upper electrode layer. As for the above-mentioned touch detecting method, the parasitic capacitance may cause the voltage Vs detected from the detecting line to become smaller, therefore reducing the detection sensitivity of the touch display panel. For the IPS-LCD touch display panel, the driving lines and the detecting lines disposed all over the entire layer may also lead to parasitic capacitances existed between the driving and detecting lines and the common and pixel electrodes which are separated, thus reducing the detection sensitivity of the touch display panel.
Based on this situation, the present invention provides a touch display panel to improve the above-motioned problems.